big bang Nucleosyntheses

The Universe's light-element abundance is another important criterion by which the Big Bang hypothesis is verified. It is now known that the elements observed in the Universe were created in either of two ways. Light elements (namely deuterium, helium, and lithium) were produced in the first few minutes of the Big Bang, while elements heavier than helium are thought to have their origins in the interiors of stars which formed much later in the bistory of the Universe. Both theory and observation lead astronomers to believe this to be the case.

Thanks to the pioneering efforts of George Gamow and his collaborators, there now exists a satisfactory theory as to the production of light elements in the early Universe. In the very early Universe the temperature was so great that all matter was fully ionized and dissociated. Roughly three minutes after the Big Bang itself, the temperature of the Universe rapidly cooled from its phenomenal 101'32 Kelvin to approximately 10^9 Kelvin. At this temperature, nucleosynthesis, or the production of light elements, could take place. In a short time interval, protons and neutrons

The Big Bang Nucleosynthesis theory predicts that roughly 250f the mass of the Universe consists of Helium. It also predicts about 0.001 Oeuterium, and even smaller quantities of lithium. The important point is that the prediction depends critically on the density of baryons (ie neutrons and protons) at the time of nucleosynthesis. Furthermore,